1 /* 2 * generic net pointers 3 */ 4 5 #ifndef __NET_GENERIC_H__ 6 #define __NET_GENERIC_H__ 7 8 #include <linux/bug.h> 9 #include <linux/rcupdate.h> 10 11 /* 12 * Generic net pointers are to be used by modules to put some private 13 * stuff on the struct net without explicit struct net modification 14 * 15 * The rules are simple: 16 * 1. set pernet_operations->id. After register_pernet_device you 17 * will have the id of your private pointer. 18 * 2. set pernet_operations->size to have the code allocate and free 19 * a private structure pointed to from struct net. 20 * 3. do not change this pointer while the net is alive; 21 * 4. do not try to have any private reference on the net_generic object. 22 * 23 * After accomplishing all of the above, the private pointer can be 24 * accessed with the net_generic() call. 25 */ 26 27 struct net_generic { 28 unsigned int len; 29 struct rcu_head rcu; 30 31 void *ptr[0]; 32 }; 33 34 static inline void *net_generic(const struct net *net, int id) 35 { 36 struct net_generic *ng; 37 void *ptr; 38 39 rcu_read_lock(); 40 ng = rcu_dereference(net->gen); 41 BUG_ON(id == 0 || id > ng->len); 42 ptr = ng->ptr[id - 1]; 43 rcu_read_unlock(); 44 45 BUG_ON(!ptr); 46 return ptr; 47 } 48 #endif 49